Running great....then not! Cavitation problem help please!

[Sandman251]

Hi had my 97' challenger out yesterday. Ran great. Then we stopped for 10 minutes. When we took back off I had a no-plane condition. The boat just plowed water at WOT. Would finally plane after about 20 seconds and perform fine while on plane. Tried 3 or 4 more times with the same results. I inspected the bilge at WOT while plowing water and observed "bubbly" water where you see the tip of my finger. We stopped at a little party store where there likely would be a lot of debris in the water, although I jumped in and did not see any obstructions.

To clarify, The bubbling water appeared to be coming from the forward part of what looks like a hose clamped boot or bellows.

What are the highest priority culprits for this condition, and does anybody have an outlet for parts or resources for step-by-step repair procedures?

Thanks a bunch!

 

[Coastiejoe]

If you have any water coming from that area, you have a defective Carbon Seal or a pin hole in the bellows. To test the carbon seal, loosen the bellows clamp that is on the hull, slide the bellows toward the carbon seal, tighten the clamp. Also put a wire tie behind the bellows where you just produced the gap. If you solve the issue by doing this, this will buy you time. You need to replace the carbon seal. It may have the O-ring style retainer under the coloar. If so, replace it with the C-Clip style..

 

[Sandman251]

If you have any water coming from that area, you have a defective Carbon Seal or a pin hole in the bellows. To test the carbon seal, loosen the bellows clamp that is on the hull, slide the bellows toward the carbon seal, tighten the clamp. Also put a wire tie behind the bellows where you just produced the gap. If you solve the issue by doing this, this will buy you time. You need to replace the carbon seal. It may have the O-ring style retainer under the coloar. If so, replace it with the C-Clip style..

Holy cow, thanks for the quick response. I was actually reading your similar response to a another post. Let me go over the procedure so I have it right.
First I'll inspect the bellows for cracking/holes. Then Loosen the hose clamp on the aft part of the bellows and slide it forward. The gap that is created I fill with a "cable" or "zip" tie so that the bellows does not tend to slide back. Am I looking for around 1/4"? Sounds like I am trying to increase the forward pressure on the forward part of the bellows?
Would it be common for the carbon seal to fail like turning off a light switch? I will say before we stopped for 10 minutes we just came off a long WOT run. Would this tend to warp the carbon seal and other associated parts?

Thanks so much for your advice!

 

[Sandman251]

I wanted to ad....The RPMs while we were plowing water were NOT 6K-7K like others have reported while cavitating. As we started to plane off, the RPMs rose slowly until we reached around 7K. Is it completely abnormal to see bubbling water coming from the bellows area, especially under full planing load? Could it be raves or something else?

 

[Bills86e]

Have you unscrewed the fuel filter and examined the fuel internal element/filter for contaminates? If you have been buying ethanol enhanced gas, your element probly disintegrated and all those trapped crap particles are now in your carburetor(s) internal filters, hence not much gas too much air, a LEAN condition. Repair this immediatly!

Bills86e

 

[Coastiejoe]

There should be an occasional drip from the face of the Carbon Seal. If it is more than a drip or not at the face of the Carbon Seal, there is an issue.. They tend to wear slowly but surely but are not an issue until they hit a specific point and it often depends on load as well. Your description of what to do is correct. By moving the bellows toward the carbon seal this put more pressure agains the carbon seal and the collar. The zip tie is solely to prevent the boot from slipping back. You may have another issue, but at the very least, tis needs to be addressed. The reason is, if water is coming in, you are also sucking air. That air is directly in line with the impeller. ANY air in the impeller area will allow for slippage. So it is not cavitation in that it is boiling the water, it is slippage in that you are moving air, not water.

 

[Sandman251]

Thanks everybody. I appreciate the input. I'll take a closer look at it this week and advise.